EL2 related deep traps in semi-insulating GaAs

Processes induced by below-the-gap illumination and related to defects having deep levels in liquid-encapsulated Czochralski semi-insulating GaAs crystals were studied. It was found that the dynamics of both optical quenching and thermal recovery (above 125 K) of thermally stimulated current signal related to six deep traps was the same as that of the EL2 related photoconductivity signal. Analysis of these results gives evidence that some of the observed deep traps in GaAs are complex defects, which might include as their constituent the EL2 defect. It means that EL2 could serve as a gettering center for other native defects and/or impurities. The proposed model is in accordance with other recently published results associating several deep traps (EL6, EL3, EL5, and EL14) with EL2.